In upwind horizontal axis wind turbines it is necessary to separate the blade from the tower sufficiently to avoid it from being able to hit the tower when the blade bends due to the effect of the wind thrust.
Furthermore, it is typical to incorporate a blade pitch change mechanism or system, which changes the blade angle, thus regulating the power collected from the wind. For this purpose, a bearing is incorporated that is partly fixed to a hub and the other part to the blade. An actuator that may be electric or hydraulic moves the blade to the appropriate angle for the wind turbine's operating conditions. To reduce the loads in the pitch actuation, it is convenient that the blade at rest is not aligned with the pitch axis.
To increase the distance of the blade to the tower, U.S. Pat. No. 4,180,369 describes a rotor configuration consisting of mounting the blades at an angle, so that the rotor describes a cone on rotating. An alternative to this solution is to make the blades forwardly curved, as described in EP1019631.
A solution that increases the distance between blade and tower whilst misaligning the longitudinal direction of the blade with respect to the pitch axis is described in DE202006013519. To implement said solution, it is necessary to cut the blade angle, maintaining the bores wherethrough the hold-down bolts pass perpendicular to the contact surface between the bearing and the blade, and which, therefore, form an angle with the longitudinal direction of the blade. The bearing is of conventional type, the hold-down bolts of the blade being placed parallel to the pitch axis and perpendicular to the contact surface between blade and bearing.